1. Field of the Invention
The present invention relates to a lens-fitted photo film unit and an assembling method for the same, and more particularly, relates to a lens-fitted photo film unit having plural taking lenses selectively set on a photographic optical axis according to each of plural modes, and a viewfinder with which a photographic object can be checked differently between the modes, and an assembling method for the same.
2. Description Related to the Prior Art
A lens-fitted photo film unit is known as a single-use camera having a simple structure for taking an exposure and pre-loaded with a photo film cassette. The lens-fitted photo film unit includes a housing and an outer belt or casing. The housing accommodates the photo film cassette. The outer belt covers the housing at least partially, and provided with information and decorative patterns. The housing accommodates a taking lens, shutter mechanism, photo film winder mechanism and the like.
There is a type of the lens-fitted photo film unit having two taking lenses disposed in a lens holder. The taking lenses have different focal lengths. A selected one of the taking lenses is set in a photographic light path by rotating the lens holder according to intention of a user. Thus, one of standard photography and a photography of a specialized mode can be selected.
JP-B 2657104 discloses the lens-fitted photo film unit of an example having a macro lens included in the taking lenses for the close-up photography, and a normal lens included in the taking lenses for the standard photography. When an externally operable member is operated, the lens holder is rotated to set either one of the macro lens and the normal lens in the photographic light path. It is possible to select one of the standard photography and the close-up photography to take an exposure.
JP-A 07-134370 discloses the lens-fitted photo film unit of an example including a first of the taking lenses for the standard photography and a second of the taking lenses having a smaller focal length for panoramic photography. When the externally operable member is operated, the lens holder is rotated to set either one of the taking lenses in the photographic light path. It is possible to select one of the standard photography and the panoramic photography to take an exposure.
In the lens-fitted photo film unit, a viewfinder has a light path positioned differently from the photographic light path. When the taking lenses are changed over, a viewfinder field region must be changed over at the same time according to an angle of frame.
In JP-B 2657104, the viewfinder field region is determined according to a photographing region of the normal lens. There is a target mark, printed on a movable member, and inserted into the viewfinder field region upon setting of the macro lens, for compensating for the parallax.
In JP-A 07-134370, a frame mark for the viewfinder field region is printed according to the photographing region of the taking lens for the standard photography. At the time of the panoramic photography, the panoramic frame mark is inserted in the light path of the viewfinder in response to rotation of the lens holder. The viewfinder field region of the viewfinder is limited panoramically.
However, the target mark and the field region mark have shortcomings in that errors are likely to occur because their visible position are shifted if a user""s eye shifts. Furthermore in the field frame mark, there is no change in the size of an object image viewed through the viewfinder even though the size of the object image to be recorded in the photo film is changed by a change of the focal length of the selected taking lens. It is impossible to check the size of the object image visually before an exposure.
It is possible to conceive the lens-fitted photo film unit changeable between the standard photography and telephotography by combining the taking lens having a long focal length. However, the taking lens having the long focal length must be in a position offset forwards from the taking lens having a short focal length. To obtain a space for shifting the taking lens with the long focal length, a lens barrel should have a shape projecting forwards. Alternatively, a projecting portion should be formed with a part of a front cover including the lens barrel.
In FIG. 11, a known lens-fitted photo film unit 140 is changeable between two taking lenses having respective focal lengths. A housing 141 of the lens-fitted photo film unit 140 includes a photo film cassette, a shutter mechanism, and the like. An outer belt 143 is wound about the housing 141 and attached to its front. A front cover 142 is one of outer covers included in the housing 141, and provided with a projecting portion 144, in which a space is kept for accommodating the two taking lenses. The projecting portion 144 has a surface curved in a manner of a quadratic curved surface. The outer belt 143 is wound about the center of the housing 141 in covering the front of the projecting portion 144.
However, a projecting amount of the projecting portion 144 increases according to an increase in the focal length of the taking lens. This results in enlarging the whole size of the lens-fitted photo film unit.
If a front surface of the projecting portion 144 is formed as a cubic curved surface for a design, looseness occurs in the outer belt, which cannot be attached neatly. There is no further variety in modifying the front surface of the projecting portion 144 than quadratic curved surfaces.
In view of the foregoing problems, an object of the present invention is to provide a lens-fitted photo film unit having plural taking lenses selectively set on a photographic optical axis according to each of plural modes, and a viewfinder with which a photographic object can be checked differently between the modes, and an assembling method for the same.
Another object of the present invention is to provide a lens-fitted photo film unit in which one of plural taking lenses have a long focal length and can be accommodated even in a compact space in an projecting portion of a body, and an assembling method for the same.
In order to achieve the above and other objects and advantages of this invention, a lens-fitted photo film unit is pre-loaded with photo film, and includes first and second taking lenses arranged in an arranging direction crosswise to a photographic optical axis, and having focal lengths different from each other. A movable lens holder supports the first and second taking lenses. An externally operable member is operable by external operation, for moving the lens holder in the arranging direction, to set the first and second taking lenses selectively on the photographic optical axis. A viewfinder optical system is settable at first and second viewfinder magnifications, and adapted to observation of a photographic field. A magnification changer mechanism is shifted in response to movement of the lens holder, for setting the viewfinder optical system at the first and second viewfinder magnifications respectively when the first and second taking lenses are set on the photographic optical axis.
The viewfinder optical system includes an objective lens, an eyepiece lens and a movable lens disposed therebetween. The magnification changer mechanism moves the movable lens along a viewfinder optical axis.
Furthermore, a front cover covers a front of the lens holder. A slot is formed in the front cover. The externally operable member is movable through the slot by external operation.
The lens holder, when in the first position, sets the first taking lens on the photographic optical axis, and when in the second position, sets the second taking lens on the photographic optical axis. Furthermore, a holder stopper mechanism prevents the lens holder from moving out of an orbit between the first and second positions.
The lens holder is rotatable about a rotational center thereof, the rotational center is disposed under the photographic optical axis. The externally operable member is disposed between the rotational center and the first and second taking lenses.
Furthermore, a shutter mechanism is actuated upon a releasing operation, for providing an exposure in the photo film. A lock mechanism allows the releasing operation if the lens holder is in the first or second position, and inhibits the releasing operation if the lens holder is between the first and second positions.
Furthermore, a first toggle spring has one end secured to the lens holder, for biasing the lens holder toward the first and second positions respectively when the lens holder is offset from a dead point toward the first and second positions.
The holder stopper mechanism includes first and second stopper walls, disposed on sides of a rotational orbit of the lens holder, for contacting the lens holder.
In another preferred embodiment, the holder stopper mechanism includes a stationary stopper pin. An arc-shaped slot or recess is formed in the lens holder, has an arc shape with reference to the rotational center, has first and second ends, for receiving insertion of the stopper pin, the first and second ends being contacted by the stopper pin, to set the lens holder in respectively the first and second positions.
Furthermore, first and second apertures are formed in the lens holder behind respectively the first and second taking lenses, the first aperture being positioned at a level in front of a level of the second aperture.
Furthermore, a light-shielded tunnel is disposed between the lens holder and the photo film, for shielding ambient light from a light path defined along the photographic optical axis. A light restricting aperture is disposed in the light-shielded tunnel, and has a size associated with effective flux for exposure through the first taking lens. An anti-reflection member is disposed on an inner face of the light-shielded tunnel and between the light restricting aperture and the photo film, for absorbing unwanted light having passed the second taking lens and an edge portion of the light restricting aperture while the effective flux for exposure through the second taking lens comes incident upon the photo film.
The shutter mechanism includes a shutter blade for opening/shutting a light path along the photographic optical axis, the shutter blade being rotatable in a blade rotating orbit. The first toggle spring is movable in a spring moving orbit disposed opposite to the blade rotating orbit with reference to the photographic optical axis.
The first toggle spring includes a coil portion. Furthermore, a support wall supports a rear of the lens holder movably. A recess is formed in the support wall, for receiving entry of the coil portion when the first toggle spring moves.
The magnification changer mechanism sets the movable lens in first and second lens positions on the viewfinder optical axis respectively when the lens holder is in the first and second positions. Furthermore, a second toggle spring has one end secured to the movable lens, for biasing the movable lens toward the first and second lens positions respectively when the movable lens is offset from a dead point toward the first and second lens positions.
The magnification changer mechanism includes a transmission lever, has a driven end and a driving end, the driven end being moved by rotation of the lens holder, for causing the driving end to move the movable lens along the viewfinder optical axis.
Furthermore, a lens stopper mechanism prevents the movable lens from moving away from an orbit between the first and second lens positions. While the lens holder is rotated toward the first and second positions, the second toggle spring starts the transmission lever to rotate with the driving end, for moving the movable lens respectively to the first and second lens positions. When the lens holder is rotated to the first and second positions, the driven end is disengaged from the lens holder.
Furthermore, a housing is pre-loaded with the photo film, for containing the first and second taking lenses, the lens holder and the viewfinder optical system. A central opening is formed in a portion of a front wall of the housing positioned at least on the photographic optical axis. An auxiliary cover member is secured to the housing to cover the central opening, and has one portion for introducing light from the photographic field to the first or second taking lens.
Furthermore, an outer sheet member covers at least a partial surface of the housing.
The auxiliary cover member is secured to the housing removably, and the externally operable member is movable on the auxiliary cover member.
The outer sheet member has at least one portion disposed between the auxiliary cover member and the housing.
The auxiliary cover member includes a cover opening for causing the first or second taking lens to appear externally on the photographic optical axis.
The auxiliary cover member is transparent and protects the first and second taking lenses.
According to another aspect of the invention, an assembling method of assembling a lens-fitted photo film unit includes the following steps. The outer sheet member is secured to the housing. After the outer sheet member is secured to the housing, the auxiliary cover member is secured to the housing.
At least a portion of the outer sheet member is disposed between the auxiliary cover member and the housing by the auxiliary cover member securing step.